The electromagnetic field around a Kerr black hole inside a current loop is sometimes used as the basis of a toy model for discussing the properties of particle orbits near astrophysical black holes. The motivation for the present paper is to correct the published solution to Maxwell’s equations with a charged current loop. Dipole approximations and closed-form expressions in the extreme Kerr limit are also presented. Using the corrected solution, it turns out that imposing a vanishing electromotive force produces a loop with a potential which is finite everywhere outside the black hole. Ring solutions can be combined into solutions with multiple rings or current discs.

We solve for the spectrum of the Laplacian as a Hamiltonian on ${\mathbb{R}}^2-\mathbb{D}$ and in ${\mathbb{R}}^3-\mathbb{B}$. A self-adjointness analysis with $\partial \mathbb{D}$ and $\partial \mathbb{B}$ as the boundary for the two cases shows that a general class of boundary conditions for which the Hamiltonian operator is essentially self-adjoint are of the mixed (Robin) type. With this class of boundary conditions we obtain “bound state” solutions for the Schroedinger equation. Interestingly, these solutions are all localized near the boundary. We further show that the number of bound states is finite and is in fact proportional to the perimeter or area of the removed disc or ball. We then argue that similar considerations should hold for static black hole backgrounds with the horizon treated as the boundary.

We develop an analytical technique to evaluate the magnetic helicity in the debris from sphaleron decay. We show that baryon number production leads to left-handed magnetic fields, and that the magnetic helicity is conserved at late times. Our analysis explicitly demonstrates the connection between sphaleron-mediated cosmic baryogenesis and cosmic magnetogenesis.

Pulsar timing experiments aimed at the detection of gravitational radiation have been performed for decades now. With the forthcoming construction of large arrays capable of tracking multiple millisecond pulsars, it is very likely we will be able to make the first detection of gravitational radiation in the nano-Hertz band, and test Einstein’s theory of relativity by measuring the polarization components of the detected signals. Since a gravitational wave predicted by the most general relativistic metric theory of gravity accounts for six polarization modes (the usual two Einstein’s tensor polarizations as well as two vector and two scalar wave components), we have estimated the single-antenna sensitivities to these six polarizations. We find pulsar timing experiments to be significantly more sensitive, over their entire observational frequency band ($\approx {10}^{-9}–{10}^{-6}\mathrm{Hz}$), to scalar-longitudinal and vector waves than to scalar-transverse and tensor waves. At ${10}^{-7}\mathrm{Hz}$ and with pulsars at a distance of 1 kpc, for instance, we estimate an average sensitivity to scalar-longitudinal waves that is more than two orders of magnitude better than the sensitivity to tensor waves. Our results imply that a direct detection of gravitational radiation by pulsar timing will result into a test of the theory of general relativity that is more stringent than that based on monitoring the decay of the orbital period of a binary system.

In a recently proposed neutrinophilic two-Higgs-doublet model, the low-energy (sub-MeV) effective theory consists of a real scalar with a vacuum expectation value of $O(0.1)\mathrm{eV}$ and three Dirac neutrinos. Other models could lead to the same low-energy theory. In this Brief Report, we study constraints on the parameter space of the model, including vacuum stability, unitarity, perturbativity, and the effects on the invisible $Z$ width. Interestingly, we find that all neutrinos become massless at temperatures above approximately 1000 K, but can find no phenomenological effects of this finding. The most direct test of the model is that it predicts that, in a galactic supernova, the energy distributions of the electron, muon, and tau neutrinos will be Fermi-Dirac with identical temperatures, unlike the conventional distributions.

We propose the signal $1b+1l+N_j+{\cancel{E}}_T$ along with appropriate selection criteria for the LHC 7 TeV run, where the number of jets ($N_j$) is $\ge 2$ or 4. These signals can complement the canonical $\mathrm{\text{Jets}}+{\cancel{E}}_T$ signature since they are sensitive to the trilinear soft breaking parameter ($A_0$) and low values of the parameter $\tan \beta$ in the minimal supergravity (mSUGRA) model. A large region of this mSUGRA parameter space within the reach of the ongoing experiments at the LHC is disfavored by the bound on the lightest Higgs boson mass ($m_h\ge 114.4\mathrm{GeV}$), unless $A_0$ has moderate to large negative values. Interestingly, part of this parameter space with $A_0\ne 0$ is also consistent with the observed dark matter relic density. A natural consequence of large $A_0$ is the existence of a light top squark (${\tilde{t}}_1$). The proposed signals primarily stem from direct ${\tilde{t}}_1{\tilde{t}}_1^{*}$ production and/or $\tilde{g}\to {\tilde{t}}_{1}t$, if all squark-gluino events are considered. A thorough analysis of the signals and the corresponding backgrounds are presented using the event generator Pythia. We finally compare the signal size for $A_0=0$ and $A_0\ne 0$.

We present a reanalysis of CDF data to extend limits on individual fourth-generation quark masses from particular flavor-mixing rates to the entire space of possible mixing values. Measurements from CDF have set individual limits on masses, $m_b^{\prime }$ and $m_t^{\prime }$, at the level of 335–385 GeV assuming specific and favorable flavor-mixing rates. We consider the space of possible values for the mixing rates and find that the CDF data imply limits of 290 GeV and greater over a wide range of mixing scenarios. We also analyze the limits from the perspective of a four-generation Cabibbo-Kobayashi-Maskawa (CKM) matrix. We find that present experimental constraints on CKM elements do not suggest further constraints on fourth-generation quark masses.

We present an approach to higher point loop integrals using Chinese magic in the virtual loop integration variable. We show, using the five point function in the important $e^{+}{e}^{-}\to f\overline{f}+\gamma$ process for initial state radiation as a pedagogical vehicle, that we get an expression for it directly reduced to one scalar 5-point function and 4-, 3-, and 2- point integrals, thereby avoiding the computation of the usual three tensor 5-pt Passarino-Veltman reduction. We argue that this offers potential for greater numerical stability.

First measurements of the decays of the three ${\chi }_{cJ}$ states to $p\overline{p}{K}^{+}{K}^{-}$ final states are presented. Intermediate $\varphi \to K^{+}{K}^{-}$ and $\Lambda (1520)\to p{K}^{-}$ resonance states are observed, and branching fractions for ${\chi }_{cJ}\to \overline{p}{K}^{+}\Lambda (1520)$, $\Lambda (1520)\overline{\Lambda }(1520)$, and $\varphi p\overline{p}$ are reported. We also measure branching fractions for direct ${\chi }_{cJ}\to p\overline{p}{K}^{+}{K}^{-}$ decays. These are first observations of ${\chi }_{cJ}$ decays to unstable baryon resonances and provide useful information about the ${\chi }_{cJ}$ states. The experiment uses samples of ${\chi }_{cJ}$ mesons produced via radiative transitions from $106\times {10}^6$ ${\psi }^{\prime }$ mesons collected in the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider.

It is shown that a string carrying a field of harmonic type can have circular vorton states of a new throbbing kind, for which the worldsheet geometry is stationary but the internal structure undergoes periodic oscillation.

We study the effective potential of a real scalar ${\phi }^4$ theory as a function of the temperature $T$ within the simplest $\Phi$-derivable approximation, namely, the Hartree approximation. We apply renormalization at a “high” temperature $T_{\star }$ where the theory is required to be in its symmetric phase and study how the effective potential evolves as the temperature is lowered down to $T=0$. In particular, we prove analytically that no second order phase transition can occur in this particular approximation of the theory, in agreement with earlier studies based on the numerical evaluation or the high temperature expansion of the effective potential. This work is also an opportunity to illustrate certain issues on the renormalization of $\Phi$-derivable approximations at finite temperature and nonvanishing field expectation value and to introduce new computational techniques which might also prove useful when dealing with higher order approximations.

The Aharonov-Bohm-Casher problem is examined for a charged particle describing a circular path in the presence of a Lorentz-violating background that is nonminimally coupled to a spinor and a gauge field. The particle eigenenergies were evaluated, showing that the LV background is able to lift the original degenerescence in the absence of magnetic field even for a neutral particle. The Aharonov-Casher phase is used to impose an upper bound on the background magnitude. A similar analysis is accomplished in a space endowed with a topological defect, revealing that both the disclination parameter and the LV background are able to modify the particle eigenenergies. We also analyze a particular case where the particles interact harmonically with the topological defect and the LV background, with similar results.

The Solar System bounds on $R^n$ gravity are often ignored in the literature by invoking the chameleon mechanism. We show that in order for the latter to work, the exponent $n$ must be ridiculously close to unity and, therefore, these theories are severely constrained.

The fate of the phantom dark energy universe in semiclassical gravity is investigated. Quantum corrections coming from massless fields conformally coupled with gravity are considered, to see if they can lead to avoidance of the big rip singularity, which shows up in a flat Friedmann-Robertson-Walker universe, filled with phantom dark energy and modeled by an equation of state of the form $p=\omega \rho$ with $\omega <-1$. The dynamics of the model are discussed for all values of the two parameters, named $\alpha >0$ and $\beta <0$, which come from quantum corrections. It is concluded that, when $-1<\frac{\beta }{3\alpha }<0$, almost all solutions develop future singularities (the corresponding scale factor and energy density go down to zero in finite time). However, when $-1>\frac{\beta }{3\alpha }$, almost all solutions describe a universe bouncing infinitely many times (an oscillating universe).

We study the constraints on the Lee-Wick Higgs sector arising from direct collider searches. We work in an effective-field theory framework, where all of the Lee-Wick partners are integrated out, with the sole exception of the Lee-Wick Higgs bosons. The resulting theory is a two-Higgs doublet model where the second doublet has wrong-sign kinetic and mass terms. We include the bounds coming from direct Higgs searches at both LEP and Tevatron using the code HiggsBounds, and show the currently excluded parameter space. We also analyze the prospects of LHC Run-I, finding that with a total integrated luminosity of $5{\mathrm{fb}}^{-1}$ and a center-of-mass energy of 7 TeV, most of the parameter space for the standard model-like $CP$-even Higgs will be probed.

Sterile massive neutrinos are a natural extension of the standard model of elementary particles. The energy density of the extra sterile massive states affects cosmological measurements in an analogous way to that of active neutrino species. We perform here an analysis of current cosmological data and derive bounds on the masses of the active and the sterile neutrino states, as well as on the number of sterile states. The so-called $(3+2)$ models, with three sub-eV active massive neutrinos plus two sub-eV massive sterile species, is well within the $95\%\mathrm{CL}$ allowed regions when considering cosmological data only. If the two extra sterile states have thermal abundances at decoupling, big bang nucleosynthesis bounds compromise the viability of $(3+2)$ models. Forecasts from future cosmological data on the active and sterile neutrino parameters are also presented. Independent measurements of the neutrino mass from tritium beta-decay experiments and of the Hubble constant could shed light on sub-eV massive sterile neutrino scenarios.

The minimal supersymmetric extension of the standard model (MSSM) is a well-motivated theoretical framework, which contains an extended Higgs sector, including a light Higgs with standard model-like properties in most of the parameter space. Because of the large QCD background, searches for such a Higgs, decaying into a pair of bottom quarks, are very challenging at the LHC. It has been long realized that the situation may be ameliorated by searching for Higgs bosons in supersymmetric decay chains. Moreover, it has been recently suggested that the $b\overline{b}$ decay channel may be observed in standard production channels by selecting boosted Higgs bosons, which may be easily identified from the QCD background. Such boosted Higgs bosons are frequent in the MSSM, since they are produced from decays of heavy colored supersymmetric particles. Previous works have emphasized the possibility of observing boosted Higgs bosons in the light Higgsino region. In this work, we study the same question in the regions of parameter space consistent with a neutralino dark matter relic density, analyzing its dependence on the nonstandard Higgs boson, slepton, and squark masses, as well as on the condition of gaugino mass unification. In general, we conclude that, provided sleptons are heavier than the second lightest neutralinos, the presence of boosted Higgs is a common MSSM feature, implying excellent prospects for observation of the light MSSM Higgs boson in the near future.

A revised formula for the inclusive cross section of a double parton scattering process in a hadron collision is suggested basing on the modified collinear two-parton distributions extracted from deep inelastic scattering. The possible phenomenological issues are discussed.

Using the holographic gauge-gravity duality, we find a solution for an isolated vortex and a vortex lattice in a $2+1$-dimensional $p$-wave superconductor, which is described by the boundary theory dual to an $SU(2)$ gauge theory in $3+1$-dimensional anti-de Sitter space. Both $p_x+i{p}_y$ and $p_x-i{p}_y$ components of the superconducting order parameter, as well as the effects of a magnetic field on these components, are considered. The isolated vortex solution is studied, and it is found that the two order parameter components have different amplitudes due to the time-reversal symmetry breaking. The vortex lattice for large magnetic fields is also studied, where it is argued that only one order parameter component will be nonzero sufficiently close to the upper critical field. The upper critical field exhibits a characteristic upward curvature, reflecting the effects of field-induced correlations captured by the holographic theory. The free energy is calculated perturbatively in this region of the phase diagram, and it is shown that the triangular vortex lattice is the thermodynamically preferred solution.

Starting from the basic path integral in phase space we reconsider the functional approach to the renormalization group flow of the one particle irreducible effective average action. On employing a balanced coarse-graining procedure for the canonical variables we obtain a functional integral with a non trivial measure which leads to a modified flow equation. We first address quantum mechanics for boson and fermion degrees of freedom, and we then extend the construction to quantum field theories. For this modified flow equation we discuss the reconstruction of the bare action and the implications on the computation of the vacuum energy density.